1. Field of the Invention
The present invention generally relates to a vertical-cavity surface emitting laser that emits laser light in perpendicular to the growing direction of an active layer, and in particular, to a modularized vertical-cavity surface emitting laser that can be bonded by flip-chip bonding.
2. Description of the Related Art
A vertical-cavity surface emitting laser has been used in a device that requires an optical interconnection structure and in various forms of laser light sources due to its low threshold current, circular light pattern, and a better choice over an edge emitting laser as it can be arranged two-dimensionally.
The vertical-cavity surface emitting laser typically includes a first mirror layer and a second mirror layer that are sequentially deposited on a semiconductor substrate, and an active layer having a multiple quantum well structure grown between the first mirror layer and the second mirror layer. When an electrical current to the active layer is applied, laser light emits in perpendicular to the growing direction of the active layer. A distributed Bragg reflector or a structure on which multi-layered dielectric materials are deposited may be used as the first mirror layer and the second mirror layer. The first mirror layer and the second mirror layer resonate the light generated from the active layer, and emit laser light having coherence of predetermined intensity and wavelength through one vertical end of the vertical-cavity surface emitting laser.
In the vertical-cavity surface emitting laser, two electrodes for supplying current may be formed on an upper portion of the vertical-cavity surface emitting laser, and on the bottom of the semiconductor substrate. However, the electrode of the vertical-cavity laser is electrically connected to an external electrode by wire bonding, causing an increase in its volume and driving voltage due to electrical loss. As a result, the vertical-cavity laser cannot be used in digital devices having a tendency towards slimness for portability.